Are you attempting to login to a public server such as Lego Universe Reborn? If so that is why you are unable to log in. That server has been down for quite a while. If you wish to play, download server 0.5.1 and run it in the background. Second go to your boot.cfg and change the authip part to „localhost“ without the „. You should be able to log in with any username and password as long as the server is running in the background.